[Audio] Molecular Conduction Workshop 2007This is the 5th in a series of annual workshops on Molecular Conduction – the prior workshops have been in W. Lafayette (2003, 2005), Evanston (2004) and Virginia (2006). The workshop has been an informal and open venue for discussing new results and key challenges. Two years ago, we expanded the theme of the workshop to include molecular-scale sensing, i.e. nano-scale sensor elements for chemical and biological sensing.http://nanohub.org/resources/2661
Sun, 02 Aug 2015 23:27:57 +0000HUBzero - The open source platform for scientific and educational collaborationThis is the 5th in a series of annual workshops on Molecular Conduction – the prior workshops have been in W. Lafayette (2003, 2005), Evanston (2004) and Virginia (2006). The workshop has been an informal and open venue for discussing new results and key challenges. Two years ago, we expanded the theme of the workshop to include molecular-scale sensing, i.e. nano-scale sensor elements for chemical and biological sensing.nanoHUB.orgsupport@nanohub.orgnoen-gbCopyright 2015 nanoHUB.orgResourcesMCW07 Impact of Porphyrin Functional Groups on InAs Gas Sensorshttp://nanohub.org/resources/3149
Porphyrin molecules are often used for sensor engineering to improve sensitivity and selectivity to specific analytes. It is important to understand how the porphyrin HOMO-LUMO levels deplete surface states during functionalization of solid state sensors. Additionally, the effect of functionalization on the analyte sensing mechanism is significant to overall gas sensor design. We have previously studied the impact of the hemin porphyrin on the sensitivity of an InAs device with respect to NO ...Porphyrin molecules are often used for sensor engineering to improve sensitivity and selectivity to specific analytes. It is important to understand how the porphyrin HOMO-LUMO levels deplete surface states during functionalization of solid state sensors. Additionally, the effect of functionalization on the analyte sensing mechanism is significant to overall gas sensor design. We have previously studied the impact of the hemin porphyrin on the sensitivity of an InAs device with respect to NO ...noband structure, devices, from outside NCN, hosted/taped by NCN@Purdue, materials science, molecular electronics, nano/bio, research seminar, sensors, surfacesMichael GarciaMichael GarciaOnline PresentationsMon, 05 Nov 2007 20:41:22 +0000/http://nanohub.org/site/resources/2007/09/03153/2007.07.19-garcia-mcw.mp3MCW07 Electronic Level Alignment at Metal-Molecule Contacts with a GW Approachhttp://nanohub.org/resources/3094
Most recent theoretical studies of electron transport in single-molecule junctions rely on a Landauer approach, simplified to treat electron-electron interactions at a mean-field level within density functional theory (DFT). While this framework has proven relatively accurate for certain systems, such as metallic point contacts, the computed conductance often substantially exceeds the measured values for organic molecules. This disagreement has raised questions about the validity of static DFT, inherently a ground state theory, for computing electronic transport properties.Most recent theoretical studies of electron transport in single-molecule junctions rely on a Landauer approach, simplified to treat electron-electron interactions at a mean-field level within density functional theory (DFT). While this framework has proven relatively accurate for certain systems, such as metallic point contacts, the computed conductance often substantially exceeds the measured values for organic molecules. This disagreement has raised questions about the validity of static DFT, inherently a ground state theory, for computing electronic transport properties.noab initio, algorithms, band structure, computational chemistry, from Berkeley, from outside NCN, hosted/taped by NCN@Purdue, materials science, molecular electronics, nanoelectronics, quantum transport, research seminar, surfacesJeffrey B. NeatonJeffrey B. NeatonOnline PresentationsThu, 06 Sep 2007 01:00:53 +0000/http://nanohub.org/site/resources/2007/09/03132/2007.07.19-neaton-mcw.mp3MCW07 A Quantum Open Systems Approach to Molecular-Scale Deviceshttp://nanohub.org/resources/3090
Experimental advances in electrically and optically probing individual molecules have provided new insights into the behavior of single quantum objects and their interaction with the nanoenvironments without requiring ensemble average. Molecular-scale devices are open quantum systems whose dynamics are intrinsically stochastic and are subject to dissipation and decoherence through system-environment correlation. New concepts and computational techniques may be needed to unravel the rich physics underlying single-molecule measurements.

In this talk, I discuss our efforts in developing quantum open systems theory of single-molecule electronics and optics, based on the concept of quantum trajectory which links measurement theory with stochastic dynamics of open quantum systems. . Experimental advances in electrically and optically probing individual molecules have provided new insights into the behavior of single quantum objects and their interaction with the nanoenvironments without requiring ensemble average. Molecular-scale devices are open quantum systems whose dynamics are intrinsically stochastic and are subject to dissipation and decoherence through system-environment correlation. New concepts and computational techniques may be needed to unravel the rich physics underlying single-molecule measurements. <br /><br />In this talk, I discuss our efforts in developing quantum open systems theory of single-molecule electronics and optics, based on the concept of quantum trajectory which links measurement theory with stochastic dynamics of open quantum systems. . nofrom outside NCN, hosted/taped by NCN@Purdue, molecular electronics, nanoelectronics, nanophotonics, quantum computing, quantum transportYongqiang XueYongqiang XueOnline PresentationsTue, 26 Feb 2008 03:02:46 +0000/http://nanohub.org/site/resources/2007/09/03234/2007.07.20-xue-mcw.mp3MCW07 Silicon Based Nanopore Sensors for Detection of DNA Moleculeshttp://nanohub.org/resources/3079
Solid-state nanopores have emerged as possible candidates for next-generation DNA sequencing devices. In this talk, we will review our recent work in development of solid-state nanopore channels that are selective towards single strand DNA (ssDNA). Nanopores functionalized with a 'probe' of hair-pin loop DNA can, under an applied electrical field, selectively transport short lengths of 'target' ssDNA that are complementary to the probe. Even a single base mismatch between the probe and the target results in longer translocation pulses and a significantly reduced number of translocation events. Our single molecule measurements allow us to separately measure the molecular flux and the pulse duration, providing a tool to gain fundamental insight into the channel-molecule interactions. The results can be explained in the conceptual framework of diffusive molecular transport with particle-channel interactions.Solid-state nanopores have emerged as possible candidates for next-generation DNA sequencing devices. In this talk, we will review our recent work in development of solid-state nanopore channels that are selective towards single strand DNA (ssDNA). Nanopores functionalized with a 'probe' of hair-pin loop DNA can, under an applied electrical field, selectively transport short lengths of 'target' ssDNA that are complementary to the probe. Even a single base mismatch between the probe and the target results in longer translocation pulses and a significantly reduced number of translocation events. Our single molecule measurements allow us to separately measure the molecular flux and the pulse duration, providing a tool to gain fundamental insight into the channel-molecule interactions. The results can be explained in the conceptual framework of diffusive molecular transport with particle-channel interactions.nobio-chemical sensing, biomolecular electronics, biosensing, DNA/Nucleic Acids, from outside NCN, from Purdue, hosted/taped by NCN@Purdue, molecular electronics, nano/bio, nanobio applications, nanopores, research seminar, sensorsSamir Iqbal, Demir Akin, Rashid BashirSamir Iqbal, Demir Akin, Rashid BashirOnline PresentationsWed, 12 Sep 2007 00:51:02 +0000/http://nanohub.org/site/resources/2007/09/03228/2007.07.19-iqbal-mcw.mp3MCW07 Exploring Trends in Conductance for Well-Defined Single Molecule Circuitshttp://nanohub.org/resources/3077
In our recent research, we have been able to measure and characterize the impact of intrinsic molecular properties on the conductance of single molecule circuits formed with amine-gold linkages. In this talk, I will review the experiments and the physical picture of the junction based on the calculations. I will then focus on three recent studies: (i) the impact of substituents on the conductance through diaminobenzene; (ii) the trends in conductance through diaminonaphthalene and diaminoanthracene as a function of the location of the amine link groups [4]; and (iii) comparison of junctions formed with amine links to those formed with methylthiol and dimethylphosphine links.In our recent research, we have been able to measure and characterize the impact of intrinsic molecular properties on the conductance of single molecule circuits formed with amine-gold linkages. In this talk, I will review the experiments and the physical picture of the junction based on the calculations. I will then focus on three recent studies: (i) the impact of substituents on the conductance through diaminobenzene; (ii) the trends in conductance through diaminonaphthalene and diaminoanthracene as a function of the location of the amine link groups [4]; and (iii) comparison of junctions formed with amine links to those formed with methylthiol and dimethylphosphine links.nocircuits, density functional theory, DFT, experiments, from outside NCN, hosted/taped by NCN@Purdue, molecular electronics, nanoelectronics, research seminarMark S HybertsenMark S HybertsenOnline PresentationsSun, 05 Apr 2009 06:49:06 +0000/http://nanohub.org/site/resources/2007/09/03157/2007.07.19-hybertsen-mcw.mp3MCW07 Modeling Charging-based Switching in Molecular Transport Junctionshttp://nanohub.org/resources/3076
We will discuss several proposed explanations for the switching and negative differential resistance behavior seen in some molecular junctions. It is shown that a proposed polaron model is successful in predicting both hysteresis and NDR behavior, and the model is elaborated with image charge effects and parameters from electronic structure calculations. This model includes the effects of conformational change, charging, and image charge stabilization.Sina Yeganeh is a graduate student ...We will discuss several proposed explanations for the switching and negative differential resistance behavior seen in some molecular junctions. It is shown that a proposed polaron model is successful in predicting both hysteresis and NDR behavior, and the model is elaborated with image charge effects and parameters from electronic structure calculations. This model includes the effects of conformational change, charging, and image charge stabilization.Sina Yeganeh is a graduate student ...noab initio, computational chemistry, devices, from Northwestern, from outside NCN, hosted/taped by NCN@Purdue, molecular electronics, nanoelectronics, nanowires, NEGF, quantum transport, research seminarSina Yeganeh, Misha Galperin, Mark A. RatnerSina Yeganeh, Misha Galperin, Mark A. RatnerOnline PresentationsWed, 05 Sep 2007 21:14:32 +0000/http://nanohub.org/site/resources/2007/09/03161/2007.07.19-yeganeh-mcw.mp3MCW07 Modeling Molecule-Assisted Transport in Nanotransistorshttp://nanohub.org/resources/3074
Molecular electronics faces many problems in practical device implementation, due to difficulties with fabrication and gate-ability. In these devices, molecules act as the main conducting channel. One could imagine alternate device structures where molecules act as quantum dots rather than quantum wires, with assembled molecular adsorbates acting as scattering centers in commercial silicon-based FETs. Molecular electronics faces many problems in practical device implementation, due to difficulties with fabrication and gate-ability. In these devices, molecules act as the main conducting channel. One could imagine alternate device structures where molecules act as quantum dots rather than quantum wires, with assembled molecular adsorbates acting as scattering centers in commercial silicon-based FETs. noballistic MOSFET, from outside NCN, hosted/taped by NCN@Purdue, materials science, molecular electronics, nanoelectronics, nanotransistors, NEGF, quantum transport, research seminar, sensorsKamil WalczakKamil WalczakOnline PresentationsTue, 06 Nov 2007 16:23:58 +0000/http://nanohub.org/site/resources/2007/09/03169/2007.07.18-walczak-mcw.mp3MCW07 Physics of Contact Induced Current Asymmetry in Transport Through Moleculeshttp://nanohub.org/resources/3073
We first outline the qualitatively different physics involved in the charging-induced current asymmetries in molecular conductors operating in the strongly coupled (weakly interacting) self-consistent field (SCF) and the weakly coupled (strongly interacting) Coulomb Blockade (CB) regimes. The CB regime, dominated by single charge effects, typically requires a computationally demanding many-electron or Fock space description.

Our analysis of several molecular Coulomb Blockade measurements reveal that many novel signatures can be explained using a “simpler” orthodox model that involves an incoherent sum of Fock space excitations and hence treats the molecule as a “metallic dot” or an “island”. This also reduces the complexity of the Fock space description by just including various charge configurations only, thus partially underscoring the importance of electronic structure, while retaining the essence of the single charge nature of the transport process.We first outline the qualitatively different physics involved in the charging-induced current asymmetries in molecular conductors operating in the strongly coupled (weakly interacting) self-consistent field (SCF) and the weakly coupled (strongly interacting) Coulomb Blockade (CB) regimes. The CB regime, dominated by single charge effects, typically requires a computationally demanding many-electron or Fock space description.<br /><br />Our analysis of several molecular Coulomb Blockade measurements reveal that many novel signatures can be explained using a “simpler” orthodox model that involves an incoherent sum of Fock space excitations and hence treats the molecule as a “metallic dot” or an “island”. This also reduces the complexity of the Fock space description by just including various charge configurations only, thus partially underscoring the importance of electronic structure, while retaining the essence of the single charge nature of the transport process.nofrom outside NCN, from Purdue, hosted/taped by NCN@Purdue, molecular electronics, nanoelectronics, NEGF, quantum computing, quantum dots, quantum transport, research seminarBhaskaran Muralidharan, Owen D. Miller, Neeti Kapur, Avik Ghosh, Supriyo DattaBhaskaran Muralidharan, Owen D. Miller, Neeti Kapur, Avik Ghosh, Supriyo DattaOnline PresentationsMon, 25 Feb 2008 23:07:08 +0000/http://nanohub.org/site/resources/2007/09/03212/2007.07.18-muralidharan-mcw.mp3MCW07 Simple Models for Molecular Transport Junctionshttp://nanohub.org/resources/3072
We review our recent research on role of interactions in molecular transport junctions. We consider simple models within nonequilibrium Green function approach (NEGF) in steady-state regime. We review our recent research on role of interactions in molecular transport junctions. We consider simple models within nonequilibrium Green function approach (NEGF) in steady-state regime. noalgorithms, from Northwestern, from outside NCN, hosted/taped by NCN@Purdue, molecular electronics, nanoelectronics, nanophotonics, NEGF, quantum dots, quantum transport, research seminar, thermal transportMisha Galperin, Abraham Nitzan, Mark A. RatnerMisha Galperin, Abraham Nitzan, Mark A. RatnerOnline PresentationsThu, 13 Sep 2007 21:20:35 +0000/http://nanohub.org/site/resources/2007/09/03216/2007.07.18-galperin-mcw.mp3MCW07 Conductance Switching in Fluorene/TiO2 Molecular Heterojunctionshttp://nanohub.org/resources/3071
Molecular junctions consisting of a monolayer of fluorene and 10 nm of TiO2 between conducting contacts exhibit a memory effect upon positive polarization of the of the TiO2 for a few milliseconds. The junction conductance increases for a period of several minutes, but can be “erased” by a millisecond negative bias pulse. This “memory” effect is attributed to a redox process in the TiO2 which generates TiIII and/or TiII, which have much higher conductance than TiO2 due to the presence of conduction band electrons. The redox process amounts to “dynamic doping” of the TiO2 layer by imposed electric field. The memory effect arises from a combination of the properties of the molecular and oxide layers, and is a special property of the molecular heterojunction configuration.Molecular junctions consisting of a monolayer of fluorene and 10 nm of TiO2 between conducting contacts exhibit a memory effect upon positive polarization of the of the TiO2 for a few milliseconds. The junction conductance increases for a period of several minutes, but can be “erased” by a millisecond negative bias pulse. This “memory” effect is attributed to a redox process in the TiO2 which generates TiIII and/or TiII, which have much higher conductance than TiO2 due to the presence of conduction band electrons. The redox process amounts to “dynamic doping” of the TiO2 layer by imposed electric field. The memory effect arises from a combination of the properties of the molecular and oxide layers, and is a special property of the molecular heterojunction configuration.nocircuits, from outside NCN, hosted/taped by NCN@Purdue, molecular electronics, nanoelectronics, research seminar, surfacesRichard L. McCreeryRichard L. McCreeryOnline PresentationsThu, 13 Sep 2007 17:17:18 +0000/http://nanohub.org/site/resources/2007/09/03220/2007.07.18-mccreery-mcw.mp3